Assay devices and the manufacture thereof

An assay sample testing device comprises a porous liquid-permeable carrier strip within a casing, the carrier including a detection zone in which an assay result is revealed by specific binding of a detectable material directly or indirectly to a binding agent immobilised in the detection zone, the casing including internal registration means which cooperatively engages with corresponding registration means associated with the carrier, for example a pin and hole, such that said detection zone within the casing is precisely located in relation to the interlocking means on the casing. During manufacture, the corresponding registration means is used to control accurate formation of the detection zone on the carrier, and accurate placement of the carrier within the casing.